Centralized selection of peers as media data sources in a dispersed peer network

ABSTRACT

A multi-source peer content distribution system transfers content files from multiple, distributed peer computers to any requesting computer. The content distribution network coordinates file transfers through a mediation system including a content catalog and a host broker system. The content catalog contains an identification of each content file, the segmented subunits of each file, and the peer caches to which the subunits have been distributed. The host broker system receives content file requests issued over a network from requesting computers. In response, manifest files identifying the request corresponding content subunits and distributed cache locations are returned. The requesting computers can then retrieve and assemble the corresponding content subunits from the peer computers to obtain the requested content file.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention is generally related to network-basedcontent delivery systems and, in particular, to a streaming mediacontent delivery system supporting multiple, concurrent, peer-basedsources of multimedia content accessible subject to central mediation

[0003] 2. Description of the Related Art

[0004] The desire for high-quality, on-demand delivery of streamingmultimedia and other rich digital content is a principal driving forcein the continued development of the broadband Internet infrastructure.Indeed, with the growth of broadband connections, the number, scale, anddiversity of multimedia content servers has rapidly increased. Streamingaudio and video files, including entertainment, news broadcasts, andinstructional programming are now sourced by a variety of mainstreamInternet sites. Content delivery through streaming media is broadlyrecognized as one of the fastest growing technologies related to theInternet.

[0005] Despite the growth in interest and use, conventional contentstreaming systems have not been cost-effective or particularly reliablein delivering high-quality content. Streaming media content, includingin particular high-quality audio and video, is naturally bandwidthintensive and fundamentally sensitive to varying delivery latencies.Whether due to transient transport overloads, functional interruptionsin the network infrastructure, or bandwidth limitations of a contentsource site, the result is uniformly perceived by a recipient as areduction in the quality of service of the content source site.

[0006] Because of the open and shared nature of the Internet, fewpractical mechanisms can ensure the uninterrupted delivery of broadbandcontent, typically consisting of multi-megabyte files, over the entiredelivery path from a source site to a recipient. Known schemes includethe use of network edge caches distributed at strategic locations withinthe network infrastructure controlled by an individual service provider.These network edge caches can be operated to significantly reduce thenetwork traffic through the local network space of the individualservice provider. Large edge caches are naturally required to store anysignificant amount of streaming media content. Implementing a usefulnumber of adequately scaled, geographically distributed edge cachesrequires a large capital infrastructure investment.

[0007] Quality of service issues within the domain of individual contentsource sites are relatively easier to manage. Over the past few years,highly scaled, geographically distributed and even multiply redundantcontent source system architectures have been developed. Conventionally,these very large-scale systems are considered a baseline requirement toensure a consistent high quality of service from the source sites. Thesesites typically employ large-scale server farms, hosting extensivelibraries of archived multimedia content, that cumulatively providesufficient throughput to enable real-time responsiveness and continuouson-demand delivery. Very high-bandwidth Internet connections withsufficient capacity to accommodate peak-demand content accessrequirements are also required.

[0008] Unfortunately, conventional content delivery networks, includingfully scaled content server systems and extensive edge cache networks,have not proven adequate to broadly ensure a high quality of service toall potential users of the systems. Ultimately, any media content mustbe delivered as an effectively continuous stream of multimedia data tothe recipient computer. The continuity of the stream must remain withinthe buffer length tolerance supported by the media player on therecipient computer. Transient bandwidth bottlenecks can certainly occuranywhere beyond the scope of a conventional content delivery network.Bottlenecks and delivery latencies can occur even within the network,particularly whenever the stream data is not immediately available in alocally accessible edge cache. Such bottlenecks in the Internetinfrastructure are unfortunately both common and unpredictable.

[0009] Transient bandwidth bottlenecks can also occur in within thecontent server system itself. The rate of content access requests ishighly variable with unpredictable demand peaks. Whenever the accessrate exceeds the capabilities of the content server system, connectionrequests, including ongoing streaming data transfers, are dropped ordelayed. Whether due to network or server bottlenecks, the resultinglatencies and gaps in the delivery of stream data packets ultimately tothe recipient are uniformly seen as source-site quality of servicefailures.

[0010] Expanding the conventional content distribution networks toprevent significant transient bandwidth bottlenecks is generallyrecognized as not practical. Due to the size and diversity of theInternet and the growing demands for streaming content delivery,significantly expanding the edge cache network coverage and the capacityof all included edge caches and streaming media source sites is simplynot cost-effective. Furthermore, the costs associated withhigh-bandwidth Internet access and server throughput grow proportionalto peak access demands, which is disproportionately greater than thegrowth of average access demands. Conventionally, a minimum of 50percent additional access and server bandwidth is required, if not more,to meet peak bandwidth requirements. This additional bandwidth, however,is unused typically in excess of 90 percent of the time. The capital andoperating cost of this additional bandwidth is therefore not directlyrecoverable. Consequently, content sites and the content deliverynetwork operators have been severely limited in being able toconsistently and profitably deliver streaming media content with a highquality of service.

[0011] Consequently, there is a clear need for a content deliverynetwork architecture that can reliably provide a high quality of serviceto content stream recipients and that is cost-effective to operate.

SUMMARY OF THE INVENTION

[0012] Thus, a general purpose of the present invention is to provide anefficient peer-to-peer content distribution network system architecturecapable of efficiently providing a high quality of service in thedelivery of multimedia data streams to end-users.

[0013] This is achieved in the present invention through a multi-sourcepeer content distribution system transfers content files from multiple,distributed peer computers to any requesting computer. The contentdistribution network coordinates file transfers through a mediationsystem including a content catalog and a host broker system. The contentcatalog contains, directly or indirectly, an identification of eachcontent file, the segmented subunits of each file, and the peer cachesto which the subunits are distributed. The host broker system receivescontent file requests issued over a network from requesting computers.In response, manifest file identifying the request corresponding contentsubunits and distributed cache locations are located and returned to therequesting computer. The requesting computers can then retrieve andassemble the corresponding content subunits from the peer computers toobtain the requested content file.

[0014] An advantage of the present invention is that content isredundantly distributed in the form of discrete segments throughout apeer storage network, permitting retrieval of segments on a bestquality-of-service basis determined relative to each computer systemthat requests a streaming media content file. Multi-source segmenteddelivery of content also distributes the transport load over multiplecontent sources while ensuring the availability of multiple sources forall segments. The perceived quality-of-service is both increased andreliably maintained.

[0015] Another advantage of the present invention is that centralizedmediation of segmented file transfers permits strategic planning of theongoing segmented file transfer load distribution. Central mediationcombined with distributed segmented file storage enables the aggregatebandwidth of the content distribution network to be optimally utilized.The complexity and cost of the central content mediation system,including the scale of the network access connections to accommodateworst case usage requirements, are greatly reduced.

[0016] A further advantage of the present invention is that themediation system can perform predictive seeding of the content deliverynetwork and adaptive modification of segment distribution in response tochanging content file demands. Historical demand patterns, peer nodeavailability and bandwidth capabilities can be used to guide thestrategic distribution of content segments throughout the contentdelivery network. Planned, periodic updates of the content distributionnetwork segment caches can be used to pre-deliver content segments tomultiple strategically selected network caches during off-hours, thusminimizing both seeding and subsequent end-user demand spikes.

[0017] Still another advantage of the present invention is that thecontent distribution network can include a multi-tiered hierarchy ofcontent segment caches, including peer cache nodes, primary contentdistribution nodes, and seeding servers. Reliable access to contentsegments is ensured by wide distribution of the content segments withinthe segment cache storage tiers and across multiple tiers.

[0018] Yet another advantage of the present invention is that thecentral mediation system can be persistently connected to and monitorthe state of the available, active peer nodes of the contentdistribution network. Changes in the availability and supportedbandwidth of nodes within the content distribution network aredynamically detected and factored into the ongoing tactical utilizationof the content distribution network as mediated by the central serversystem.

[0019] Still another advantage of the present invention is that thedistribution of content segments is actively maintained by the mediationserver system. The distribution of content segments within the contentdelivery network, which is continuously subject to redistribution as aconsequence of content use requests, is tracked and managed by themediation server system to strategically adapt the distribution patternto optimally match demand patterns.

[0020] A yet further advantage of the present invention is thatproprietary content is continuously protected by a combination ofencryption and digital signatures applied to the content files and tothe individual content file segments. The mediation server systemmaintains the integrity of the content file segments throughout theoperations of file segment transport, cache storage, and streaming fileassembly and playback. The integrity of content within the contentdistribution system is thus ensured by the management function of themediation server system.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] These and other advantages and features of the present inventionwill become better understood upon consideration of the followingdetailed description of the invention when considered in connection withthe accompanying drawings, in which like reference numerals designatelike parts throughout the figures thereof, and wherein:

[0022]FIG. 1 is a block diagram of a content distribution networkorganized in accordance with a preferred embodiment of the presentinvention;

[0023]FIGS. 2A and 2B provide detail views of the segmentation of astreaming media content file in accordance with preferred embodiments ofthe present invention;

[0024]FIG. 3 is a block diagram of a peer network client systemconstructed in accordance with a preferred embodiment of the presentinvention;

[0025]FIG. 4 is a block diagram of a peer network mediation serversystem constructed in accordance with a preferred embodiment of thepresent invention;

[0026]FIG. 5 is a flow diagram of a streaming media content filetransfer executed with respect to a peer network client system inaccordance with a preferred embodiment of the present invention; and

[0027]FIG. 6 provides a detailed flow diagram of the adaptive requestprocess implemented in a peer network client system constructed inaccordance with a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0028] The content distribution network (CDN) of the present inventionprovides a comprehensive system solution to delivering streaming mediaand other digital content files to end-user systems with a consistent,high quality of service. The end-user systems participate in adistributed network of peer computer systems, organized into a tieredset of content sources, that store and, on request, selectively forwardcontent to any other peer computer system within the network. Thedistribution of content and the coordination of content requests ismediated through a centralized server system, which maintains adirectory catalog of the available content and of the location of thecontent within the network.

[0029] In the preferred embodiments of the present invention, each unitof content, typically represented by a content file, is segmented intodiscrete parts that are each uniquely identified in the catalogmaintained by the mediation server system. Multiple copies of eachsegment are preferably distributed to cache stores maintained throughoutthe network to ensure redundant sources of segments for any requestingpeer computer system. The distribution of segments within the network ofcaches is determined by the mediation server system. While entire setsof segments may be distributed to individual peer computer systems, themediation server system can also operate to ensure that only fragmentaryportions of content units are stored by individual peer computersystems. Through fragmentary storage, the effective security of thecorresponding content units is fundamentally increased. The redundantdistribution of segments permits transfer of the entire set of segmentsto a requesting peer with an assured high quality of service.

[0030] The mediation server system preferably manages the transfer ofcontent segments within and between the various storage tiers of contentdistribution network, including content seeding peer computer systems,dedicated content distribution platforms, and end-user client nodecomputer systems. The seeding peers preferably operate as the source ofnew content segments for distribution to the content distributionnetwork and as ultimate backup sources for segments of requestedcontent. The dedicated content distribution platforms preferably operateas a middle tier for content distribution, affording a greater fan-outof the transfer load in distributing content segments to the end-userclient systems. These content distribution platforms may also be used asdedicated sources of proprietary or other content that for licensing orother reasons will not be distributed for persistent storage in theend-user tier of content caches. Finally, the end-user client node tieris typically a highly heterogenous collection of typically independentlyoperated computer systems, each used to host a segment storage cache andto participate on an ad-hoc basis in the content distribution network.Client node systems may support caches of varying size, networkconnections of varying capacity, and be available on independentschedules.

[0031] Requests for selected content units and cache content updaterequests are submitted to the mediation server through preferablypersistent network connections. Manifest lists of the segments may bereturned directly or indirectly through an identification of a locationwithin the peer network where a copy of the manifest list is stored.Based on a manifest list, content segments are independently requestedby and transferred to nodes of the content distribution system. The peerdriven segment retrieval process is cooperatively monitored by themediation server and, as needed, alternate source locations for segmentsare provided. Information on the performance of individual peers and thepatterns of requests are collected and evaluated on a generally dynamicbasis for the generation of request manifest lists. This information isalso utilized as a basis for the generation of cache update manifestlists, used to control the background transfer and controlling thestorage distribution of content segments throughout the network tooptimize the delivery of content in anticipation of demand.

[0032] A preferred architecture of a CDN system 10, consistent with thepresent invention, is shown in FIG. 1. The CDN system 10 preferablyincludes a central server system 12 and a peer content storage network14. While logically operating as a centralized system, the variousserver computer systems that cooperatively function as the centralserver system 12 can be remotely located, duplicated, and scaled asneeded for management, performance, and commercial requirements. Theoperational functions of the central server system 12 include thepreparation, including segmentation, of new content for publication, thedistribution and management of content segments throughout the peercontent storage network 14, monitoring the effective performance andactual content segment transfers between various peer nodes within thecontent storage network 14, and responding to content and cache updaterequests.

[0033] In the preferred embodiments of the present invention, newcontent is initially prepared through a content publisher system 16 byencoding or transcoding a new content file or other unit of content toone of several defined media content formats. The currently preferredformats include the Microsoft® WMA streaming media and the MotionPicture Experts Group MPG3 formats. Other formats can be equivalentlyprocessed and used. The content file is then encrypted through a licenseencoding server. In the preferred embodiments of the present invention,a Microsoft digital rights management (DRM) encryption system isutilized to encrypt the content and subsequently manage the serving oflicenses by a license server 20. A content unit identifier, uniquelycorresponding to the encrypted, encoded content file, and the DRMgenerated license key are provided to the license server 20.

[0034] Encrypted, encoded content files are segmented by a contentsegmentation server 22. As illustrated in FIG. 2A, representing a firstpreferred embodiment, a content file 24 is divided into segments 26_(1−N), each with a defined segment size, generally within the range of25 kilobytes and 2 megabytes and typically on the order of 100kilobytes. Each segment is then assigned the unique content unitidentifier 28 and a segment sequence identifier 30, permitting aparticular content file 24 to be reassembled in order from a collectionof the content segments 26 _(1−N). The resulting construction of namedsegments 32 are then transferred to a seeding peer server 34 and storedin a seeding cache 36 for subsequent distribution further into the peercontent storage network 14. Preferably, the seeding peer server 34 isconsidered part of the peer content storage network 14.

[0035] Segment catalog records 38 _(1−N) are generated in correspondencewith the named segments 32 _(1−N). For a named segment 32 ₂, thecorresponding segment catalog record 38 ₂ includes a copy of the contentunit identifier 28 and segment sequence identifier 30 of the namedsegment 32 ₂. A security value 40, based on the data content of thesegment 26 ₂, and a field 42 permitting storage of one or more locationidentifiers are also included in the segment catalog record 38 ₂.Preferably, the security value 40 is an MD5 hash, multi-byte checksum,or other data value signature of the segment 26 ₂ sufficient tosubsequently authenticate the data integrity of the segment 26 ₂.

[0036] The location identifiers are preferably surrogate clientidentifiers assigned to the peer nodes within the content storagenetwork 14. These surrogate client identifiers are preferably resolvableby the central server system 12 to peer network storage cache addresses,preferably in a uniform resource identifier (URI) form. The current URIof a client node can be determined whenever the client node reconnectswith the central server system 12. In resolving a location identifierfor a client computer system that is currently unavailable, a null URIis returned. Preferably, location identifiers uniquely correspond topeer nodes. In an alternate embodiment, where the location identifierfurther identifies a particular cache store of named segments 32, thelocation identifier revolves to a URI identifying a node and cachecombination.

[0037] The segment catalog records 38 are stored to a content catalogdatabase maintained by a database server 44. As created, the locationfield 42 of the segment catalog records 38 initially contain only thelocation identifier of the seeding peer 34. Whenever a named segment 32is copied to or deleted from a segment cache within the storage contentnetwork 14, the location field 42 the corresponding segment catalogrecord 38 is updated to reflect the current set of location identifiersspecifying the content caches from which the segment can be obtained.

[0038] In response to a content unit request, the corresponding segmentcatalog records 38 are prepared and returned as part of a contentmanifest. In preparing the content manifest, the individual segmentcatalog records 38 are expanded by resolving the location identifiers tothe complete URIs for the referenced named segments 32. The requestingpeer thus receives the necessary information to directly retrieve andvalidate the named segments 32 needed to reconstruct the requestedcontent file 24.

[0039] A second preferred embodiment of content segmentation andcataloging is shown in FIG. 2B. As before, named segments 32 are createdfrom the content file 24. Groups of segments, preferably representingcontiguous portions of the content file 24 are transferred to theseeding peer 34 and subsequently distributed as segment groups tocontent segment caches within the content storage network 14.

[0040] A content manifest file 38′ is generated in combination with thenamed segments 32. The content manifest file 38′ includes the uniquecontent unit identifier 28, a list 30′ of the segment sequenceidentifiers for the named segments 32, and the security values 40′ foreach of the named segments 32. In the preferred embodiment of thepresent invention, the content manifest file 38′ is distributed as animplied first member of each segment group. Alternately, the contentmanifest file 38′ may be distributed separately through the seeding peer34 to the content segment caches of selected, typically highavailability peer computer systems within the content storage network14.

[0041] A series of manifest catalog records 38″_(X) are also created incombination with the named segments 32 and manifest content file 38′.Each manifest catalog record 38″_(X) is established for a respectivesegment group for the content file 24. A manifest catalog record 38″_(X)includes the unique content unit identifier 28, a list 30″ of thesegment sequence identifiers for the corresponding sequence group ofnamed segments 32, a manifest security value 40″, and one or morelocation identifiers 42″ that specify the content caches storing thecorresponding segment group of the content file 24.

[0042] The manifest security value 40″ is preferably an MD5 hash,multi-byte checksum, or other data value signature of the contentmanifest file 38′ sufficient to subsequently authenticate the integrityof the content manifest file 38′. Where the content manifest file isseparately distributed, an additional set of one or more locationidentifiers are included with the identification identifiers 42″ tospecify available content segment caches that store copies of thecontent manifest 38′. The location identifiers 42″ as stored by thecontent catalog are updated as the content manifest 38′ and segmentgroups are copied between and deleted from content segment-caches withinthe content storage network 14.

[0043] In response to a content unit request, the manifest catalogrecords 38″_(X) are returned to the requesting peer computer system. Thelocation identifiers 42″ are expanded URIs prior to returning themanifest catalog record 38″. The requesting peer computer system canthen obtain a copy of the manifest content file 38′ and validate thecopy against the manifest security value 40″. Individual named contentsegments 32 can then be requested from any peer computer system thatpersistently stores an encompassing segment group.

[0044] This second preferred embodiment of content segmentation andcataloging is presently preferred based on the reduced load incurred bythe central server system 12. The content manifest file 38′, due atleast to the number and size of included security values 40′, may be anappreciable fraction of the size of the corresponding content file 24.Distribution and retrieval of the content manifest file 38′ from thecontent storage network 14 greatly reduces the file transfer loadimposed on the central server system 12.

[0045] In the preferred embodiments of the present invention, thecentral server system 12 supports persistent connections establishedbetween the remotely distributed nodes of the peer content storagenetwork 14 and a persistent network proxy server 46. The persistentconnections are preferably initiated by a client node of the peerconnection storage network 14 to a defined TCP/IP socket supported bythe persistent network proxy server 46. These persistent connections areutilized to permit peer nodes to supply the central server system 12with a then current surrogate client identifier, report status andperformance information from the peer connection storage network 14 tothe central server system 12 and to request and obtain manifests.

[0046] In the absence of specific activity, as an ongoing backgroundactivity, active client nodes utilize the persistent connections tosignal a continuing availability to participate in segment datatransfers within the peer content storage network 14. In response toactivity, client nodes also report outbound segment transfer load levelsand other performance indicators affected by ongoing peer networkparticipation, including any communication failures that may occur.Client nodes actively performing inbound segment data transfers fromother nodes of the peer connection storage network 14 preferably alsoutilize the persistent connections to report network data transfer ratesand latency information against other identified client nodes. Thepersistent network proxy server 46 preferably collects and records thisstatus and performance information in a network status databasemaintained by the database server 44. The data contained within thenetwork status database, in effect, represents a peer network map usefulto plan use of the peer content storage network 14.

[0047] Content unit requests, as submitted by the client nodes, aredirected through the persistent network proxy server 46 to a host brokerserver 48. Each content unit request provides the unique content unitidentifier for the requested content unit. A search of the contentcatalog database locates the catalog records corresponding to thecontent segments necessary to construct the requested content unit. Thereferenced locations identifiers are evaluated against the performanceinformation represented by the network peer network map to select anoptimal, redundant set of content segments. This evaluation preferablyreflects a load-balancing of the ongoing segment data transfer demandson the potentially participating nodes of the peer connection storagenetwork 14. The evaluation also considers the reported network datatransfer rates between the requesting client node or similarly situatedclient nodes and the potentially participating nodes. As a product ofthe evaluation, the host broker server 48 can produce a content recordslisting a set of content segments, collectively representing therequested content unit, that can be retrieved from specified locationswithin the peer content storage network 14. The specified locationsdetermined by the host broker server 48 thus collectively represent amediated balancing of the need to broadly distribute the system-widecontent segment transfer load across the available peer network nodesand ensure effectively uninterrupted delivery of each requested contentunit to the requesting peer nodes.

[0048] Preferably, a complete content manifest-based workingspecification of the requested content unit is dynamically constructedby a requesting client node. The content manifest file is retrievedeither from another client node or through the host broker server 48.Based on the segment catalog records 38 _(X) or the segment group indexrecords 38″_(X), including the content unit and segment sequenceidentifiers, segment security values, and the expanded locationidentifiers 42, 42″, the working content manifest is constructed by theclient node. Preferably, the expanded location identifiers are presentedin a priority ordered by segment sequence number and relativelypreferred location from which to transfer the segment as determined bythe performance and load-balancing evaluation performed by the hostbroker server 48.

[0049] The distribution of named content segments 32 throughout the peerconnection storage network 14 is, in the preferred embodiments of thepresent invention, actively performed by the peer nodes of the peerconnection storage network 14. Named content segments 32 are placed by acontent segmentation server 22, individually or as members of segmentgroups, in the content segment cache 36 of one or more seeding peerservers 34. The named content segments 32 are then dispatched typicallythrough the Internet 50 in response to peer node requests to variousdedicated content distribution network platforms 52, client nodeplatforms 54, 56, and potentially other seeding servers 34.

[0050] Preferably, all peer nodes within the peer connection storagenetwork 14 implement content servers, such as peer node applications 58,60, to support the network transfer of named content segment 32 betweenrespective local content segment caches 36, 62, 64. The progressivedistribution, including redistribution, of named content segments 32 ispredominately effected by the peer node applications 58, 60 and anysecondary seeding peer servers 34 directly requesting sets of namedcontent segments 32 for storage in the associated content segment caches36, 62, 64. Additional distribution and redistribution of named contentsegments 32, again individually or as members of segment groups, followsfrom the on-demand transfer of the named content segments 32 of contentunits requested by individual client nodes. As named content segments 32are received by a requesting client node 54, a copy is stored at leasttransiently in the associated content segment cache 64 pending streamingto a client media player 66.

[0051] Strategic control over the distribution of the named contentsegments 32 is preferably performed by a manifest manager server 68. Inaccordance with the present invention, at least the dedicated contentdistribution network platforms 52 and client node platforms 54, 56periodically issue cache update manifest requests to the central serversystem 12 through the persistent connections with the network proxyserver 46. Cache update manifest requests are also preferably issued oneach initiation of a persistent connection. A content unit request mayalso be treated as a cache update manifest request.

[0052] In the preferred embodiments of the present invention, themanifest manager server 50 determines a distribution pattern of namedcontent segments 32 based on an ongoing analysis of the peer networkmap, a log of the recent content unit requests and segment transfers, asstored by the broker server 48 to the database server 44, and optionallyconstraints and hints provided by central server system 12administrators. In general, the goal of the analysis is to maximize theavailability of named content segments 32 to likely requesting peernodes over network connections of sufficient, reliable bandwidth,subject to the segment cache storage size, load limitations, andreported peer node relative network connection bandwidth of individualpeer nodes. While, in a present implementation, this dynamic analysis isperformed on a progressive batch basis, a near real time evaluation andanalysis of the collected data is preferred.

[0053] Constraint information may be employed in the analysis torestrict the distribution of the named content segments 32 of particularcontent units to defined dedicated content distribution networkplatforms 52, as may be externally determined appropriate for certaintypes of content. Constraint information may also specify language orother meta-data attributes of content units that can be activelyconsidered in the analysis to determine an appropriate distributionpattern for content units. Other constraint information may be providedto specify periods within which specific content units will beavailable, permitting controlled, progressive distribution of contentsegments prior to a release date and subsequent retirement after a closedate.

[0054] Hinting information is preferably provided to the manifestmanager 70 to peremptorily drive the distribution of named contentsegments 32. The hinting information may be specified in terms of thepriority and prevalence of the distribution of named content segments 32corresponding to particular content units. The prevalence hints mayindicate desired levels of redundant copy distribution over geographicand other domains. Alternately, or in addition, the hinting informationmay be specified by associating empirical and historically-deriveddistribution patterns with specified content units. Particularly in thecase of historically-derived patterns, the distribution of previouslydistributed content units can be used as a reference for projecting thelikely demand distribution of newly released content units.

[0055] The central server system 12 preferably includes one or more webservers 72, which may be geographically distributed, to providetypically end-user accessible interfaces for the selection of contentunits. The web servers 72 connect through network connections to thedatabase server 44 to obtain browsable and searchable lists of thecontent units available through the mediating operation of the centralserver system 12. In accordance with the present invention, select webservers 72 may be designated as the sole or limited selection source fordefined content units. Consequently, these select web servers 72 may beoperated as the apparent source of proprietary or branded content, atleast from the perspective of end-users, yet obtain the full use andbenefit of the CDN system 10 in distributing the proprietary and brandedcontent units.

[0056] A preferred embodiment of a peer application 60 is detailed inFIG. 3. Executed as a component of a system application on a clientplatform 54, a system manager 80 implements the top-level procedurallogic of the peer application 80. A network connection agent 82 providesa persistent proxy interface to the network proxy 46, supporting thebidirectional transfer of control messages 84, such as content unit andcache management requests, and data 86, including request and cacheupdate manifests. Named content segments 32 are requested and received,in a preferred embodiment of the peer application 60, through an HTTPclient component 88 from remote peers. A file receiver component 90,supervised by the system manager 80, performs the detailed transfercontrol of data files and named content segments 32 through theconnection agent 82 and HTTP client 88 relative to a local contentsegment cache 64.

[0057] As each named content segment 32 is received, a security value isregenerated based on the data of contained segment 26 and comparedagainst a corresponding security value 40, 40′, as provided in thecurrent request or cache update manifest. A comparison failure with thesecurity value 40, 40′ indicates a corrupt named content segment 32,which is discarded. Valid named content segments 32 are stored to acontent segment cache 64 under the management control of a cache managercomponent 92 and the system manager 80. Preferably, the content segmentcache 64 is encrypted subject to a DRM license. Accesses to the namedcontent segments 32 require an encryption key acquired through a licensemanager component 94, which provides an interface 96 to a conventionalDRM client 68 and, as required through the connection agent 82, to theremote license server 20.

[0058] The peer application 60 preferably implements an HTTP server 98to provide conventional streaming content connectivity to an externalclient media player 66 or other streaming media content client. Astreaming content component 100 coordinates between the system manager80, for initial set-up of the content streaming session, and the cachemanager 92, for the ordered retrieval of named content segments 32corresponding to a requested content unit. Retrieved named contentsegments 32 are progressively passed by the streaming server 100 fromthe local content segment cache 64 to the HTTP server 98 for relay to amedia player 66.

[0059] The HTTP server 98 also supports named content segment 32transfer requests from other peer nodes of the peer connection storagenetwork 14. A segment server component 102 is utilized to manage namedcontent segment 32 transfers, subject to segment transfer sessionmanagement performed by the system manager 80. The transfer of namedcontent segments 32 to the HTTP server 98 is coordinated by the segmentserver 100 with the cache manager 92 for selection of the requestidentified named content segments 32 from the content segment cache 64.

[0060] A preferred architecture 110 of a content delivery networkcentral server system 12, exclusive of segment preparation andpublication components, is shown in FIG. 4. A conventionalhardware-based network connection load balancer 112 supports a scalableset of CDN server systems 114, 116. Each CDN server systems 114, 116implements a set of executable server components that are implemented onone or more conventional network connected server computer systems. TheCDN server systems 114, 116 share access to a CDN database 118configured to store OLTP accessible data and an archive databaseproviding storage of recently logged and historical data that can beused for analytic and reporting purposes.

[0061] A client proxy component 120 maintains the direct socketconnections for the persistent client sessions established against theactive peer nodes of the peer connection storage network 14. A startupmessage is received by the client proxy component 120 from each peernode upon joining the peer connection storage network 14. Completionmessages are received as different processes are completed by the peernodes.

[0062] A proxy manager 122 monitors the connections established with theclient proxy component 120 to maintain a data structure representing thepeer nodes that are currently active and accessible. Periodic statusmessages are exchanged to actively monitor the state of the connectedpeer nodes. Failures in the status exchange are preferably analyzed withthe result of redirecting a peer node to another CDN server system 114,116, which may be able to establish a more reliable network connection,or the connection is disconnected and the peer node is identified asinactive.

[0063] A client session component 124 establishes defined contexts forcommunications with each of the peer nodes connected to the client proxy120. Within each context, information is gathered through variousprogress, status, and logging messages received from the peer nodes. Thecollected information, as well as the activity state information managedby the proxy manager, is stored to the CDN database 118 for subsequentuse in performance analysis and activity reporting.

[0064] A host broker component 126 receives, through the client proxy120, the peer node content unit requests. Through OLTP databaseaccesses, the host broker determines an optimal set of peer nodes fromwhich the requesting peer node can download the named content segments32 corresponding to the requested content unit. Preferably, the hostbroker selects all active peer nodes that store named content segments32, individually or in segment groups, of the requested content unit andthen orders identical copies of the named content segments 32 by theload level of the source peer node and the evaluated connection speedbetween the source and requesting peer nodes. The top segment catalogrecord 38, 38″ entries for named content segments 32 are selected andprovided in one or more request catalog messages that are then returnedto the requesting peer.

[0065] A file session component 128 actively monitors the ongoing namedcontent segment 32 download and streaming operations of the individualpeer nodes within corresponding client sessions. In conjunction with thehost broker component 126, a unique file session identifier is providedin each content unit request manifest. Unique file session identifiersare also provided in each cache update manifest. When a streamingcontent unit transfer is terminated, the peer node provides a sessionfinished message to the file session component 128. A file sessionfinished message is also provided when a peer node has completed acontent segment cache update, based on a provided cache update manifest.

[0066] A file session finished message includes the request or cacheupdate manifest corresponding file session identifier and informationdetailing the required transfer time, number of source peer nodes used,and other statistically relevant information. Network communicationsfailures with particular source peer nodes and other error conditionsare also reported. The acquired information is stored to the CDNdatabase 118 for subsequent use in performance analysis and activityreporting.

[0067] A cache manifest manager 130 is responsible for establishing thedistribution of named content segments throughout the peer connectionstorage network 14. The collected information stored by the CDN database118 is periodically evaluated on a daily or shorter basis. Newlyavailable content units, as represented by stored segment catalogrecords 38, are considered in the evaluation. An updated distributionplan is ultimately produced and stored by the cache manifest manager 130to the CDN database 118.

[0068] A peer cache update manager 132 is responsive to cache updatemanifest requests, as periodically issued by the peer nodes. Based onthe segment distribution plan determined by the cache manifest manager130 and preferably further qualified by recognition of the ongoing namedcontent segment 32 transfers dynamically reported to the file sessioncomponent 128, a cache update manifest specific to the requesting peernode is generated and returned.

[0069] A license manager component 134 is responsive to license requestmessages issued by client nodes in connection with content unitrequests. The request manifest, in addition to providing a requisite setof segment catalog records 38, preferably identifies the type oflicensing encryption, if any, applied to the requested content unit. Alicense request message includes the request corresponding content unitidentifier 28, a license location identifier, which specifies thelicensing authority for the requested content and requesting clientnode, and the license type identifier.

[0070] The specified license type permits the license manager 134 tovalidate the requested content unit license against the typicallyexternal licensing authority. In the preferred embodiments of thepresent invention, the license manager 134 utilizes a conventionalMicrosoft digital rights manager. Where validated, a license key isgenerated by the license manager 134 and provided to a license server136. The license is thus available to the client media player 66 for usein decrypting the streaming media content unit as received through theclient peer application 60. A license response message is also returnedthrough the client proxy 120 to the requesting peer node in response tothe license request message. The license response message eitheracknowledges the availability of the license key or provides avalidation failure explanation.

[0071] The preferred process 140 implemented by a client peerapplication 60 is shown in FIG. 5. In connection with the execution ofthe peer application 60, a client media player 66, Web browser or otherclient application, executed on the client platform 54, permits anend-user to select and login 142 to a chosen Web server 72. Preferably,a list of available content units is displayed for selection 144 by theend-user. Based typically on an end-user selection, a content unitrequest is issued 146 to the CDN server system 114 currently supportingthe persistent connection to the peer application 60. The content unitrequest is brokered 148 and a request manifest 150 is returned.

[0072] Upon receipt of the request manifest, the client peer application60 determines whether an encryption license applies to the requestedcontent unit. A license validation 154 is obtained where required. Thesegment catalog records 38, 38″ provided by the request manifest areparsed and corresponding named content segment 32 transfer requests areprogressively issued 156 to the segment catolog record 38, 38″identified peer nodes. As the requested named content segments 32 arereceived 158, the integrity of each named content segment 32 is checked160. Valid named content segments are preferably at least transientlystored 162 to the content segment cache 64. An updated cache updatemanifest provided in combination with the request manifest can determinewhich named content segments 32 are to be persistently retained in thecontent segment cache 64. Named content segments 32 that fail theintegrity check are re-requested from the same or an alternate peernode.

[0073] In the preferred embodiments of the present invention, once atleast the initial named content segment 32 has been received, streaming164 of the requested content unit is enabled to the attached clientmedia player 66. As permitted by the client media player 66, Web browseror other client application, a new content unit can be selected 144 atany time, terminating the current transfer, and causing a new contentunit request to be issued 146.

[0074] Periodic updates of the content segment cache 64 are scheduled bythe client peer application 60. Cache update requests are preferablyissued 166 automatically by the peer application 60 to the currentlyconnected CDN server system 114. A cache update manifest is generated168 and returned 170 to the requesting client peer application 60. Thecache update manifest is parsed by the client peer application 60 toidentify any named content segments 32, as specified by correspondingsegment catalog records 38, that are not currently stored by the contentsegment cache 64. Requests for the non-resident named content segmentsare issued 156 and the named content segments 32 are received 158 andstored 162 to the content segment cache 64.

[0075] In an alternate embodiment of the present invention, the cacheupdate manifest provides meta-information that is used by the clientpeer application 60 to qualify cache update operations. The cache updatemanifest meta-information is utilized to specify the schedule of cacheupdate requests and the location of the CDN server system 114, 116 touse as the target of the next cache update request. The meta-informationmay also be provided to specify a delay schedule for issuance of namedcontent segment 32 transfer requests. This allows the cache updatemanager 132 to fully mediate the data transfer load on the peer contentstorage network 14 both in terms of selecting the transfer source peernodes utilized and the temporal distribution of the load imposed onthose nodes. Such mediation is particularly valuable to optimallyschedule the load placed on the seeding peers 34 and dedicated CDNplatforms 52 particularly where the peer content storage network 14includes a large number of peer nodes.

[0076] The managed client peer process 180 of named content segmentrequest and retrieval is shown in greater detail in FIG. 6. The contentsof request and cache update manifests, including meta-information, areinitially parsed 182 upon receipt of the manifests. Deferred operationsare preferably handled through a periodic re-parsing of the manifests atthe deferred time intervals. In anticipation of the receipt of new namedcontent segments 32 beyond a client platform 54 defined cache size,named content segments 32 no longer identified in the current cacheupdate manifest are deleted 184 from the content segment cache 64.

[0077] Preferably, multiple named content segments 32 are requested 156concurrently from the peer content storage network 14. Each concurrentlyrequested named content segment 32 is also redundantly requested frommultiple peer node locations. The total number of concurrent namedcontent segment 32 transfers allowed is a dependent on the maximumacceptable load permitted on the client platform 54. Excluding theredundant transfers, a default limit is set at four concurrent transfersof unique named content segments 32. As redundant copies of namedcontent segments are received 158, the transfer bandwidths of each aremonitored. Once a reasonably stable gauge of the transfer bandwidths canbe determined, adjusted potentially for different transfer start timesand the anticipated remaining length of the named content segment 32,only the highest bandwidth transfer for each named content segment 32 ismaintained. A failure to complete any of these remaining transfers isdetected 186. A severe reduction in the transfer bandwidth is alsopreferably treated as a transfer failure. Redundant requests for thesame named content segment 32 are again reissued 188 to multiple peernode locations determinable from the manifests.

[0078] Named content segments 32 are stored 162 to the content segmentcache 64 as received 158. A security value for the segment data may beaccumulated as the named content segment 32 is received or computed oncethe named content segment 32 once the transfer is completed. This actualsecurity value is then compared 190 to the security value 40 provided inthe corresponding segment catalog record 38. On a comparison failure,the received named content segment 32 is deleted from the contentsegment cache 64. Redundant requests for the named content segment 32are again reissued 188.

[0079] Preferably, detailed information, including the connectionlatency, average bandwidth and reliability of transferring named contentsegments 32 relative to the requesting client platform 54, is collectedby the client peer application 60. Information detailing transferfailures and data integrity failures, along with the identity of thepeer nodes participating in the failed transactions, is also collected.This performance information is reported to the connected CDN serversystem 114, 116, preferably in connection with the transfer completionof each content unit transfer and cache update.

[0080] Thus, an efficient peer-to-peer content distribution networksystem architecture capable of efficiently providing a high quality ofservice in the delivery of multimedia data streams to end-users has beendescribed. While the present invention has been described particularlywith reference to operation over the public Internet, the presentinvention is equally applicable to the distribution over other publicand private communications networks. Additionally, the present inventionis also applicable to the rapid and efficient distribution of digitalinformation that may have use other than as streaming media content.

[0081] In view of the above description of the preferred embodiments ofthe present invention, many modifications and variations of thedisclosed embodiments will be readily appreciated by those of skill inthe art. It is therefore to be understood that, within the scope of theappended claims, the invention may be practiced otherwise than asspecifically described above.

1. A content distribution system supporting the transfer of a contentfile present on a plurality of peer computers to a recipient computer,said content distribution network comprising: a) a content catalogcontaining an identification of a content file and a plurality oflocation identifiers, wherein each location identifier includes anidentification of a peer computer and of a named subunit of said contentfile; and b) a control processor, coupled to said content catalog andcoupleable through a network connection to a recipient computer, whereinsaid control processor, responsive to a request identifying said contentfile provided by said recipient computer, provides a content filemanifest to said recipient computer, said content file manifestincluding said plurality of location identifiers; whereby said recipientcomputer can retrieve and assemble corresponding named subunits of saidcontent file from said peer computers to obtain said content file. 2.The content distribution system of claim 1 further comprising aperformance database, coupled to said control processor, containingperformance information for said peer computers, wherein said controlprocessor provides said content file manifest with an ordered listing ofsaid plurality of location identifiers, and wherein said controlprocessor determines said ordered listing based on said performanceinformation.
 3. The content distribution system of claim 2 wherein saidcontent file manifest provides multiple location identifiers for saidnamed subunits and wherein said ordered listing provides a preferenceorder for the retrieval of said named subunits by said recipientcomputer.
 4. The content distribution system of claim 3 wherein saidcontrol processor is further coupleable to said recipient computer toreceive update performance information, wherein said control processorprovides for the storage of said update performance information in saidperformance database.
 5. The content distribution system of claim 4wherein said update performance information includes activityinformation with respect to said recipient computer and a predeterminedone of said peer computers.
 6. A content distribution system comprising:a) a peer computer network including a plurality of segment data cachesthat provide for the distributed storage of named content segments,wherein said plurality of segment data caches have associated cachelocation identifiers, said peer computer network being responsive tonamed segment requests including named segment identifiers to providecorresponding named content segments; b) a content broker computersystem including a content catalog that provides for the storage of anamed content identifier in association with a plurality of namedcontent segment identifiers further associated with a plurality of cachelocation identifiers, said content broker computer system beingresponsive to a broker request including said named content identifierto provide said plurality of cache location identifiers selectivelyordered with respect to said plurality of named content segmentidentifiers; and c) a request computer system coupleable through acommunications network to said content broker computer system to providesaid broker request and to said peer computer network to provide segmentrequests for said plurality of named content segments respectivelyassociated with selected cache location identifiers determined based onthe selective ordering of said plurality of cache location identifierswith respect to said plurality of named content segment identifiers. 7.The content distribution system of claim 6 wherein said request computersystem is operative to provide segment requests to said peer computernetwork to progressively obtain said named content segmentscorresponding to said named content identifier.
 8. The contentdistribution system of claim 7 wherein said content broker provides saidrequest computer system with a manifest presenting preference orders ofcache location identifiers for respective ones of said plurality ofnamed content segments.
 9. A method of operating a content distributionnetwork to support the retrieval of a streaming content file, saidmethod comprising the steps of: a) distributing a plurality of namedcontent segments, collectively representing a predetermined streamingcontent file, among a plurality of peer caches, wherein a portion ofsaid named content segments are multiply distributed among saidplurality of peer caches; and b) responding to a request for saidpredetermined streaming content file by providing a retrieval listidentifying said plurality of named content segments, said listincluding an identification of the distribution of said plurality ofnamed content segments; whereby said plurality of named content segmentscan be retrieved from among said plurality of peer caches to obtain saidstreaming content file.
 10. The method of claim 9 further comprising thestep of generating said retrieval list with a plurality of locationlists, wherein each said location list identifies, with respect to apredetermined named content segment, a subset of said plurality of peercaches to which said predetermined named content segment wasdistributed.
 11. The method of claim 10 wherein said step of generatingprovides for an ordering of the identification of said subsets of saidplurality of peer caches.
 12. The method of claim 11 further comprisingthe step of collecting performance information with respect to saidplurality of peer caches and wherein said step of generating providesfor said ordering based on said performance information.
 13. The methodof claim 12 further comprising the step of cataloging the locations ofsaid plurality of named content segments as distributed among said peercaches.
 14. The method of claim 13 further comprising the step ofsegmenting said predetermined streaming content file into said pluralityof named content segments.
 15. A content distribution system supportingthe delivery of streaming media content files over a communicationsnetwork to a recipient computer system, said content distribution systemcomprising: a) a catalog of predetermined content files, said catalogincluding a listing of content file segments, wherein predeterminedpluralities of said content file segments correspond to saidpredetermined content files; b) a predictive content distribution systemoperative to distribute copies, including multiple copies, of saidcontent file segments to a plurality of peer computer systems, saidpredictive content distribution system being coupled to said catalog toassociate peer system identifiers with said content file segments toreflect the distribution of said content file segments to said peercomputer systems; c) a peer computer management system coupleable tosaid plurality of peer computer systems and operative to monitor theavailability of said content file segments as distributed to saidplurality of peer computer systems; and d) a request broker systemcoupleable through said communications network to receive a content filerequest from a recipient computer system, said request broker systemproviding, based on the availability of said content file segments asdetermined by said peer computer management system, a manifest ofcontent file segment identifiers and associated peer system identifiers;whereby said recipient computer system can utilize said manifest toobtain the content file segments corresponding to the content fileidentified by said content file request.
 16. The content distributionsystem of claim 16 wherein said peer computer management systemdynamically monitors said plurality of peer computer systems.
 17. Thecontent distribution system of claim 17 wherein said request brokersystem dynamically generates said manifest in response to said contentfile request.
 18. The content distribution system of claim 18 whereinsaid peer computer management system maintains activity and capabilityinformation with respect to said plurality of peer computer systems andwherein request broker system is responsive to said activity andcapability information in generating said manifest.
 19. A method ofobtaining streaming media content files over a communications network,said method comprising the steps of: a) issuing, over a communicationsnetwork, a content request for a predetermined content file to a hostcomputer system; b) receiving a manifest from said host computer system,said manifest including a list of content segments corresponding to saidpredetermined content file, said list including a peer cache locationidentifier for each said content segment; and c) requesting, over saidcommunications network, a first plurality of said content segments froma second plurality of peer caches identified by said peer cache locationidentifiers corresponding to said first plurality.